Suction muffler for a hermetic compressor

ABSTRACT

A suction muffler for a hermetic compressor, comprising a hollow body (10) affixing a gas duct (20) which is defined by a gas inlet portion (21) having an inner end (21a) internal to said muffler body and an outer end (21b) external to said muffler body and in fluid communication with a suction inlet tube (8) provided in the hermetic shell (1) of the compressor, and a gas outlet portion (22) having an inner end (22a) internal to said muffler body and an outer end (22b) external to said muffler body and connected to a suction orifice, which is provided in the head (5) of a cylinder disposed inside the shell (1) and where is mounted the suction muffler, the extension of the gas duct (20) internal to the hollow body (10) being spaced from the walls thereof.

FIELD OF THE INVENTION

The present invention refers to a suction muffler for a hermeticcompressor of the reciprocating type used in refrigeration systems.

BACKGROUND OF THE INVENTION

The prior art reciprocating hermetic compressors are, as a rule,provided with suction acoustic dampening systems (acoustic filters)inside the shell, with the function of attenuating the noise generatedduring the suction of the refrigerant fluid.

One of the causes which reduces the efficiency of the compressors usingthe present acoustic mufflers is the overheating of the gas being drawn.During the time elapsed between the entrance to the compressor and theadmission into the cylinder thereof, the gas temperature is increased,due to the heat transferred from the several hot sources existing insidethe compressor. The temperature increase causes an increase in thespecific volume and consequently a reduction of the refrigerant massflow. Since the refrigerating capacity of the compressor is directlyproportional to the mass flow, reducing said flow results in efficiencyloss.

It is well known that the thermal insulation of the gas being drawn by ahermetic compressor during its travel inside the hermetic shell of saidcompressor, from the suction inlet tube to the suction orifice, has asignificant effect in relation to the increase of the refrigeratingcapacity and compressor efficiency. Among the means used to provide thethermal insulation, the more effective one is the use of an acousticmuffler in the form of a suction chamber of plastic material, providedwith a tube to conduct gas from within the hermetic shell towards thesuction orifice in the cylinder head. Said muffler, when the assembly ismounted, is suspended in relation to the body of said chamber (U.S. Pat.No. 4,755,108). The distribution of volumes and tubes and respectiveopenings in the acoustic muffler is what characterizes, acoustically,the dampening effect of the noise generated in the gas suction. In orderthat the noise be dampened, the tube which conducts the gas to thesuction chamber should be provided with openings communicating theinside of said tube with the internal volumes of the muffler. It is thuscharacterized, in the same assembly, a sequence of tubes disposed inseries. The various tube sections are disposed in such a way as toprovide a direction of the gas being drawn, avoiding the mixture of thiscooler gas being drawn with the hotter gas found inside the chambervolumes.

In one known solution (U.S. Pat. No. 4,755,108), the construction of theacoustic muffler allows small leaks to occur in the connections of thetwo parts that normally form the tube. Said leaks, in more seriouscases, substantially reduce the muffler efficiency in acoustic terms.There is also an additional complication related to the manufacturingprocess, owing both to the number of pieces involved (usually four) andto the usually more complex geometry of said pieces, resulting from thelittle space available inside the hermetic shell of the compressor.

One way used to overcome such deficiency, also known in the prior art(U.S. Pat. No. 4,960,368) is based on the configuration of the tubes andvolumes defined in the muffler body, which reduces the number of pieces,without impairing the acoustic characteristic of the muffler.Nevertheless, in this solution there is some loss in the performancerelated to the heat conducted from the muffler body to the gas. Thisoccurs as a function of the contiguity of the faces of the tube whichconducts the gas to the cylinder with the internal invironment of thecompressor, which is at a higher temperature.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a suction acousticmuffler for a hermetic compressor, which presents the advantages of theknown solutions and which uses a gas flow directed during suction andthermically insulated from the hottest regions of the muffler.

Another object of the present invention is to provide a muffler with theabove cited characteristics, which is obtained with a small number ofcomponents (two plastic pieces), without using complex geometries andwhich can be easily produced and mounted.

These and other objectives are achieved through a suction muffler for ahermetic compressor including a hermetic shell and having a suctioninlet tube for gas admission therewithin, and a suction orifice which isprovided in the head of a cylinder disposed inside the shell and whereis mounted the suction muffler, said muffler comprising a hollow bodyaffixing a gas duct which is defined by a gas inlet portion having aninner end internal to the muffler body and an outer end external to saidmuffler body and in fluid communication with the suction inlet tube, anda gas outlet portion having an inner end internal to the muffler bodyand an outer end external to said muffler body and connected to thesuction orifice, the extension of the gas duct internal to the mufflerbody being spaced from the walls thereof.

According to the present invention, since there is a spacing of the gasduct in relation to the walls which define the substantially hermeticbody of the muffler and consequently in relation to the hottest parts ofthe compressor, there is a reduction in the heating of the gas beingdrawn with a consequent improvement in terms of refrigerating capacityand efficiency, as compared to the prior art known solutions. In thissolution, the acoustic dampening principle is reactive, which isadvantageous in terms of efficiency. Moreover, the present solutionallows the use of longer tubes, increasing the acoustic attenuation ofthe chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below, with reference to the attacheddrawings, in which:

FIG. 1 is a schematic longitudinal vertical sectional view of a hermeticcompressor of the reciprocating type;

FIG. 2 is a schematic perspective view of the acoustic mufflerconstructed according to the present invention before the assembly ofits component parts;

FIG. 3 is a schematic perspective view of the acoustic muffler of FIG. 2in its mounted condition, partially illustrating the inside of its body;and

FIG. 4 is a schematic perspective view of the head and the suctionsystem of the compressor.

BEST MODE FOR CARRYING OUT THE INVENTION

The acoustic muffler of the present invention is used in a hermeticcompressor of the reciprocating type comprising a shell 1, which ishermetic and inside which is suspended, e.g. by springs, amotor-compressor unit including a cylinder block 2, which lodges insidea cylinder a piston 3 that reciprocates within said cylinder 22, drawingand compressing the refrigerant gas when driven by the electric motor.

Said cylinder has an open end, which is closed by a valve plate 4affixed to said cylinder block 2 and provided with suction and dischargeorifices. Said cylinder block 2 further carries a head 5, which ismounted onto said valve plate 4 and which defines internally therewith asuction chamber 6 and a discharge chamber 7, which are maintained inselective fluid communication with the cylinder through the respectivesuction and discharge orifices. This selective communication is definedby opening and closing said suction and discharge orifices by therespective suction and discharge valves.

Shell 1 further carries a suction inlet tube mounted in an admissionorifice, which is provided at shell 1 and opened to the inside thereofand through which arrives the cool gas to be drawn, e.g. by a suctionpipe, which is external to said shell 1 and which is coupled to anevaporator of a refrigeration system to which the compressor is mounted.In this construction, the gas arriving to shell 1 is admitted to theinside of a suction acoustic muffler, to be described below, which ismounted in front of the suction chamber 6, in order to attenuate thenoise generated by the movement of the suction valve, avoiding orreducing the excitements of the cavity ressonances.

According to the present invention, the suction muffler comprises aclosed hollow body 10 of a thermo-insulating material which isexternally mounted to the head 5 and which affixes a gas duct 20, whichextension internal to said hollow body 10 is spaced from the walls ofthe latter, said gas duct 10 defining a gas inlet portion 21 and a gasoutlet portion 22.

According to the present invention, the spacing from a substantial partof the extension of the gas conduct 20 in relation to the inner walls ofthe hollow body 10 minimizes the heat transfer, received from thecompressor, to the gas duct 20 through the hollow body and consequentlyto the cool gas being drawn to the suction chamber 6. The gas duct 20 isdefined in order that, during the compressor operation, the gas which isbeing drawn maintains fluid communication with the inside of theinternal chamber of the hollow body 10, dampening suction noises withouthowever having its temperature altered to an extent that impairs the gasrefrigeration state.

The gas inlet portion 21 has an inner end 21a opened to the inside ofthe hollow body 10 and an outer end 21bin fluid communication with thesuction inlet tube 8, whereas the gas outlet portion 22 has an inner end22a and an opposite end 22b connected with the suction orifice of thehead 5.

In a non-illustrated solution, when the suction is direct or direct andhermetic between the suction inlet tube and the suction orifice of thehead 5, the outer end 21bof the gas inlet portion 21 is directly coupledby appropriate means to said suction inlet tube. In this solution, thegas flow coming from the evaporator of the refrigeration system isadmitted, without interruption, directly to the cylinder inside, beforebeing compressed in said cylinder and discharged in a condenser of therefrigeration system.

In the illustrated construction, the gas inlet portion 21 and gas outletportion 22 are structurally spaced from each other, each of saidportions having its respective inner end 21a, 22a opened towards aportion of the hollow body 10 spaced away from the region thereof thatcarries said gas inlet and gas outlet portions 21, 22 of the gas duct20. In other possible solutions, the gas duct 20 is defined in a singlepiece, having the inner end of each said gas inlet and gas outletportions physically connected to each other and maintaining openings forfluid communication with an internal volume of the hollow body 10.

In a constructive option of the present solution, the hollow body 10comprises two pieces which are attachable to each other by appropriatemeans, at least one of said pieces defining openings for the passage ofthe gas inlet and gas outlet portions 21, 22. Nevertheless, it should beunderstood that the present invention also foresees other constructionsin which the hollow body is formed in a single piece incorporating thegas duct 20.

According to the drawings, one of the pieces of the hollow body definesa cover 11, which is trespassed by the gas inlet and gas outlet portions21, 22 of the gas duct 20, to be affixed to a fixing opening 12 which isprovided at the other of said hollow body pieces and which defines abase portion 13 for the hollow body 10, said fixing opening 12 receivingand affixing the cover 11.

In the illustrated solution, the cover 11 is provided with the openingsfor the passage of the gas inlet and gas outlet portions 21, 22 of thegas duct cited above, preferably incorporating said portions. In thisconstruction, the cover 11 has a closing surface 14 where the passageopenings cited above are provided.

From the peripheral edge of said closing surface 14 there is projected,orthogonally to said closing surface 14, a peripheral flange 15provided, for example, with locking means for affixing said cover 11 tothe base portion 13, when the muffler of the present invention ismounted. In this construction, the peripheral flange 15 fits into thefixing opening opening defined at the base portion 13 of the hollow body10. The connection of the parts may be achieved, for example, bywelding, gluing or also by using clamps, the latter option beingpreferred in terms of reliability and cost relationship.

In the solution of the present invention, the suction muffler beingdescribed is mounted suspended to the cylinder block 2, by appropriatelyaffixing the outer end 22b of the gas outlet portion 22 to the suctionorifice.

According to the present invention, the fluid communication between theinner end of each of the inlet and outlet portions 21, 22 of the gasduct 20 occurs through a deflector, which is formed by at least one ofthe parts defined by the cover 11 and base portion 13 of the hollow body10 and which is adjacent to said inner ends 21a, 22a in order to directthe gas flow that is being drawn from the inner end 21a of the gas inletportion 21 to the inner end 22a of the gas outlet portion 22 of the gasduct 20. According to a solution of the present invention, the deflectoris defined by part of the hollow body portion that is spaced from theopening for affixing the base portion 13 thereof and located between theinner ends 21a and 22a of each of the gas inlet and outlet portions 21,22 of the gas duct 20. In a variant of this solution, part of thedeflector is further defined by a dividing portion 16, extending fromthe cover 11 towards the inner end of each of the gas inlet and outletportions 21, 22 of the gas duct 20 parallely to the axis thereof andwhich has, for example, an inverted "T" profile.

In the illustrated construction, the dividing portion 16 extendsorthogonally from the closing surface 14 and divides the inside of thebase portion 13 of the hollow body 10 in two gas volumes, in order todampen the suction noise of said gas.

According to the present invention, the outer end 21bof the gas inletportion 21 is projected in order to define a volume in the gas inletportion, which is illustrated with a rectangular cross section, althoughit may have any cross section, and which serves as a reservoir of coolergas. Said solution is usually employed in order to maintain in a staticcondition a certain amount of cooler gas adjacent to the muffler gasinlet for the moment in which the gas begins to be drawn to the suctionchamber. Such effect is important in view of the intermittent characterof the gas flow established during suction in a reciprocatingcompressor, avoiding the occurrence of flow recirculations whichfacilitate the mixture of the drawn gas with the gas (hotter gas) insidethe shell.

We claim:
 1. A suction muffler for a hermetic compressor, including a hermetic shell (1) and having a suction inlet tube (8) for gas admission therewithin and a suction orifice which is provided in the head (5) of a cylinder disposed inside the shell (1) and where is mounted the suction muffler, characterized in that said muffler comprises a hollow body (10) affixing a gas duct (20) which is defined by a gas inlet portion (21) having an inner end (21a) internal to said muffler body and an outer end (21b) external to said muffler body and in fluid communication with the suction inlet tube (8), and a gas outlet portion (22) having an inner end (22a) internal to said muffler body and an outer end (22b) external to said muffler body and connected to the suction orifice, the extension of the gas duct (20) internal to the muffler body being spaced from the walls thereof.
 2. A suction muffler, as in claim 1, characterized in that the hollow body (10) comprises two pieces, at least one of said pieces defining openings for the passage of the gas inlet and gas outlet portions (21, 22) of the gas duct (20).
 3. A suction muffler, as in claim 2, characterized in that one of said pieces of the hollow body (10) comprises a cover (11) which is trespassed by the gas inlet and gas outlet portions (21, 22) of the gas duct (20) and which is attachable to a fixing opening (12) defined at the other of said pieces of the hollow body (10).
 4. A suction muffler, as in claim 1, characterized in that the inner end (21a, 22a) of each of the gas inlet and gas outlet portions (21, 22) of the gas duct (20) is opened to a portion of the hollow body which is spaced from the fixing opening of the latter.
 5. A suction muffler, as in claim 4, characterized in that it comprises a deflector which is formed by at least one of the parts defined by the cover (11) and base portion (13) of the hollow body (10) adjacent to the the inner end (21a, 22a) of each of the gas inlet and gas outlet portions (21, 22) of the gas duct (20), in order to direct the gas flow from the inner end (21a) of the gas inlet portion (21) towards the inner end (22a) of the gas outlet portion (22) of the gas duct (20).
 6. A suction muffler, as in claim 5, characterized in that the deflector is defined by the portion of the hollow body (10) which is spaced from the fixing opening (12) defined at the base portion (13) thereof and between the inner ends (21a, 22a) of each of the gas inlet and gas outlet portions (21, 22) of the gas duct (20).
 7. A suction muffler, as in claim 6, characterized in that the cover (11) incorporates a dividing portion (16) which extends towards the inner end (21a, 22a) of each of the gas inlet and gas outlet portions (21, 22) of the gas duct (20) parallely to the axis thereof and which defines dampening volumes for the gas inside the hollow body (10).
 8. A suction muffler, as in claim 7, characterized in that the dividing portion (16) has an inverted "T" profile, defining part of the deflector between the inner ends (21a, 22a) of each of the gas inlet and gas outlet portions (21, 22) of the gas duct (20). 